Molecular pathogenesis of human coronaviruses

National Institute Of Allergy And Infectious Diseases

Investigators

Abstract

Since early 2020, the COVID-19 pandemic, caused by SARS-CoV-2, has ravaged the world. Consequently, we decided to focus a portion of our efforts on human coronaviruses, like SARS-CoV-2 and the Middle East Respiratory Syndrome coronavirus or MERS-CoV. Both MERS-CoV and SARS-CoV-2 are high consequence viral pathogens with the capacity to cause severe human disease, and SARS-CoV-2 has established a raging pandemic. This project will apply pre-existing expertise against these pathogens. Cellular mechanisms modulating replication of high consequence human coronaviruses. As a result of the SARS-CoV-2 pandemic and a necessary shift in research focus to coronaviruses, Dr. Dylan Flather and his collaborators are applying genome-wide screening strategies to better describe the host factors of this virus family. The identification and characterization of proviral host factors through genome-wide screens as described for TBFVs, above, has also been applied to Middle East Respiratory Syndrome (MERS) coronavirus. Collectively, the group has defined proviral host factors for six of the seven known human coronaviruses with the goal to identify pan-coronavirus host factors that could be used to develop treatments for novel coronaviruses. Our validation studies have identified a single pan-coronavirus host factor called Transmembrane Protein 41B (TMEM41B). Interestingly, other recently published MERS genome-wide screens have shown very limited overlap with the results from our screen, suggesting that the identification of factors shared across screens using different viruses may not reveal obvious shared host factors. Indeed, aside from TMEM41B, no factor was consistently determined to be proviral for the six coronaviruses that we and our collaborators have tested. However, through performing pharmacological inhibition studies we have begun to identify cellular pathways that are commonly targeted by a wide range of coronaviruses. This suggests that focusing on the protein-level to identify similarities in coronavirus replication may offer too narrow a focus and that considering protein functionalities more broadly, as parts of complexes or metabolic pathways, offers more biological relevance. Finally, we have also performed genome-wide screens in a more physiologically relevant lung-derived cell line and are currently analyzing that data in an effort to reveal cell type dependent and cell type independent MERS host dependency factors. This work is being prepared for publication. Antiviral Treatments. Our lab has antiviral libraries containing 900 antiviral compounds. A small subset of these compounds will be screened as potential treatments for CoV infection. Compounds will be chosen based on prior efficacy against other viral pathogens used by our group. Immunotoxins as SARS-CoV-2 Therapeutics. In collaboration with Dr. Seth Pincus at Montana State University, Ms. Offerdahl has performed experiments to examine the potential of immunotoxins as a treatment for SARS-CoV-2 infections. Dr. Pincuss lab has produced several SARS-CoV-2 antibody-ricin A chain conjugations with the intent to discretely kill SARS-CoV-2 infected cells. Unfortunately, only modest effects were seen using the conjugated antibodies and, in some cases, the ricin A chain conjugated to the antibody showed less efficacy than the neutralizing antibody alone. We speculate this may be due to steric hindrance. This work may be packaged into a future publication from Dr. Pincuss HIV lab work but a stand alone manuscript is unlikely